Among the important performance parameters of automotive finish coatings are smoothness, gloss and distinctness-of-image. The currently used automotive top coating based on a hydroxyl-containing acrylic resin and an amino resin is good enough to provide a finish coat satisfactory in appearance, weather resistance, physical properties and the like. However, the recent aggravation of atmospheric pollution and the consequent acid rain destroying woods and ecology in general, for instance, are presenting serious social problems and under the circumstances the automotive body coated with the above coating material is not sufficiently resistant to surface corrosion or aging. The finishes on articles used outdoors are also etched or suffer blushing and staining under the influence of acid rains. Therefore, the development of a coating film excellent in acid resistance has been earnestly sought. Aside from the above problems, the finish coat on the exterior surface of the car body is liable to be marred, for example by car-washer brushes, to impair its surface appearance and, therefore, mar resistance is also an important quality parameter that must be improved.
The primary object of the present invention is to provide a top coating composition capable of yielding a cured film with remarkably increased acid resistance without being compromised in appearance, weather resistance and physical properties.
The inventors of the present invention found, after assiduous and diligent research to overcome the above-mentioned disadvantages of the prior art coating composition, that the above object can be accomplished by providing a coating composition designed to insure the presence of benzene rings in a proportion of 13 to 40% by weight in a cured film containing a specified microparticulate polymer. The present invention has been developed on the basis of the above finding.